<template>
  <div>
    <div class="layout-content">
      <transition :name="transitionName">
        <keep-alive v-if="$route.meta.keepAlive">
          <router-view></router-view>
        </keep-alive>
        <router-view v-else></router-view>
      </transition>
    </div>
  </div>
</template>
<script>
export default {
  name: 'App',
  data() {
    return {
      transitionName: ''
    }
  },
  watch: {
    //使用watch 监听$router的变化
    $route(to, from) {
      //如果to索引大于from索引,判断为前进状态,反之则为后退状态

      if (to.meta.index > from.meta.index) {
        //设置动画名称
        this.transitionName = 'slide-left'
      } else {
        this.transitionName = 'slide-right'
      }
    }
  }
}
</script>
<style lang="scss" scoped>
// https://blog.csdn.net/qq_33236453/article/details/79110485
.slide-right-enter-active,
.slide-right-leave-active,
.slide-left-enter-active,
.slide-left-leave-active {
  will-change: transform;
  transition: all 300ms;
  position: absolute;
}
.slide-right-enter {
  opacity: 0;
  transform: translate3d(-100%, 0, 0);
}
.slide-right-leave-active {
  opacity: 0;
  transform: translate3d(100%, 0, 0);
}
.slide-left-enter {
  opacity: 0;
  transform: translate3d(100%, 0, 0);
}
.slide-left-leave-active {
  opacity: 0;
  transform: translate3d(-100%, 0, 0);
}
</style>
